This application claims the priority of German application 199 01 300.4, filed in Germany on Jan. 15, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a steering system provided for motor vehicles with a steering wheel that can be operated on the driver's side, a steering control assembly for motorized steering control of steered vehicle wheels, a steering angle setpoint generator operated by the steering wheel, a steering angle actual value sensor actuated by the steered vehicle wheels, a control system which actuates the steering control assembly as a function of a setpoint-actual value comparison of the steering angle, a manual force control device that exerts a restoring force on the steering handle, in correlation with the forces that develop between the steered vehicle wheels and the steering control assembly, as well as a control travel of the steering handle correlated with the changes in the steering angles of the steered vehicle wheels.
Steering systems of the type described above are being developed at the current time. In other words, the "steer by wire" concept is being implemented in contrast to conventional steering systems, no forced coupling is provided during normal operation between the steering handle or steering wheel and the steered vehicle wheels; instead, the steered vehicle wheels and the steering handle are coupled effectwise with one another by only a control system. A manual force control device serves to generate a steering resistance in the steering handle or steering wheel and to adjust the steering handle or steering wheel similarly to the steered vehicle wheels on the basis of steering movements produced by disturbing forces. Therefore, the manual force control device produces a feedback of the steering forces acting on the steered wheels as well as the steering movements of these wheels to the steering handle or steering wheel.
In the event of a problem with the control system or system parts cooperating therewith, a hydraulic or mechanical emergency system is provided which automatically becomes effective if a problem occurs, with the result that a hydraulic or, as in previous steering systems, a mechanical forced coupling is created between the steering handle and the steered vehicle wheels.
A goal of the invention is to provide an advantageous design for an axially adjustable steering wheel in a steering system of the type recited at the outset.
This goal is achieved according to the invention by virtue of the fact that the manual force control device is connected drivewise with the steering wheel by an axially stationary shaft part which is connected axially displaceably and nonrotatably with another shaft part mounted axially and radially in a jacket tube at its end facing the steering wheel and that the jacket tube is guided axially displaceably in a relatively stationary housing part and is held without play by spring clamping.
The invention is based on the general idea to provide a housing that receives at least the parts of the shaft train on the steering wheel side for a shaft train that is axially adjustable and permits axial control of the steering wheel between the steering wheel and the manual force control device, said housing participating in the axial control of the shaft train and thus supporting a part of the shaft train axially and radially on the steering wheel side at a constant distance from the steering wheel, said support having a high degree of resistance to vibration because the housing parts that are adjustable relative to one another are held relative to one another without play by spring clamping.
The invention takes into account the fact that on the one hand, axial adjustability of the steering wheel is desirable for reasons of comfort, and on the other hand vibrations or oscillations of the steering wheel can be avoided with particularly high reliability in a steering system of the type described at the outset since these oscillations and vibrations can result in corresponding fluctuations in the steering angle setpoint signals from the steering angle setpoint generator actuated by the steering wheel. This would be associated with corresponding control of the steering control assembly, with the consequence that the steering control assembly would attempt to follow the constant changes in the steering angle setpoint and could even amplify the vibrations and oscillations of the steering wheel. This is avoided in the invention.
According to a preferred embodiment of the invention, provision is made for the housing to have a guide tube integral with the housing for the jacket tube and for the guide tube to have radial recesses spaced axially apart for flexible pressure bodies which clamp the jacket tube radially in the guide tube.
In an especially advantageous embodiment of the invention, preferably two pressure bodies and recesses are provided that are spaced axially apart from one another, are offset with respect to one another in the circumferential direction of the guide tube, and in particular are opposite one another diametrically in the axial view of the guide tube.
This design ensures that even when manufacturing tolerances are high, there is an extraordinarily strong connection between the guide and jacket tubes; for this purpose, it is merely necessary to make the spring forces for the pressure bodies sufficiently powerful. In particular, it is advantageous that wobbling movements of the jacket tube in the guide tube are reliably suppressed by the above arrangement of pressure bodies.
It is also advantageous for the manual force control device to be connected with the steering wheel by a rotating rod which connects an axially stationary first shaft part with an axially stationary second shaft part which is axially displaceably and nonrotatably connected with the other shaft part, with the second shaft part being made tubular and the rotating rod being located essentially inside this shaft part and with the end of the second shaft part facing the first shaft part being mounted radially on an end piece of the rotating rod that is connected with the first shaft part and the other end of the second shaft part being connected nonrotatably and permanently with the other end of the rotating rod.
Here, the rotating rod also serves to connect the ends of the first and second shaft parts facing one another radially immovably relative to one another, with the first shaft part additionally possibly being connected radially to a stationary housing.
In addition, reference is made regarding the preferred invention embodiments to the claims as well as the following explanation of the invention on the basis of the especially preferred embodiments of the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.